Different forms of the same gene are Called alleles.
The cell has two sets of each chromosome; one of the pair is derived from the mother and the other from the father. The maternal and paternal chromosomes in a homologous pair have the same genes at the same loci, but possibly different alleles.
A gene is a locus (or region) of DNA which is made up of nucleotides and is the molecular unit of heredity
Haploid is the term used when a cell has half the usual number of chromosomes. A normal eukaryote organism is composed of diploid cells, one set of chromosomes from each parent.